Failover embed to lib after dist

[timkpaine]

Looks like we've hit a weird case with voila where we need to grab phosphor. The problem is libembed only checks unpkg for dist/index.js, but phosphor builds into lib/index.js. Is it possible to failover to lib here if the call to dist 404s?

[timkpaine]

phosphor 404: https://unpkg.com/@phosphor/[email protected]/dist/index.js
phosphor 200: https://unpkg.com/@phosphor/[email protected]/lib/index.js

[timkpaine]

voila-dashboards/voila#116

[timkpaine]

@jasongrout @maartenbreddels @SylvainCorlay open to suggestions for other fixes as well

[timkpaine]

Root cause is unrelated to this (voila-dashboards/voila#122) but we've had this issue with other stuff in the past, so still worth considering ( see this issue)

[timkpaine]

Closing as unfixed in case someone happens on this later, I'm gonna use phoila which supports installed bundles